Towards a revison of the dairy cow's standard for nitrogen production: justification and what are consequences for soil link rate of dairy farms. At present, the dairy cow's standard of nitrogen production in Walloon region is 90 kg per year. This standard is used to calculate the "soil link rate" of farms, a balance between the organic nitrogen to be spread on land and the quantity legally authorized considering grassland and arable land area. This standard is appreciably lower than that fixed by other member states and was criticized by the European Commission during the negotiations having ended in the second program of sustainable nitrogen management. Further to new studies, it seems that the gaseous loss of nitrogen averages in buildings and during the storage is weaker than the 15% value which was used to justify this 90 kg standard. It also seems that there are big differences of average dairy production and average rate of urea according to the agricultural regions and consequently that regional production standards correspond better to the reality. On basis of these mean values, the dairy cow's annual productions of nitrogen vary between 81 kg per year in grassy region of Fagne and 99 kg per year in Haute Ardenne and in grassy region from Liege. For the Walloon region in general, the average production is 94 kg per year. The adoption of different values of dairy cow's nitrogen production by region would lead to an increase of 8% of the soil link rate of dairy farms in Haute Ardenne and of 7% in grassy region from Liege and a decrease of 7% in grassy region of Fagne.